The present invention relates to disc drive data storage systems and, more particularly, to a method of fabricating a leading edge taper on a recording head slider.
Disc drives of the "Winchester" type are well known in the industry. Such drives use rigid discs which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the air bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the air bearing surface, air compression along the air flow path causes the air pressure between the disc and the air bearing surface to increase which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to lift and fly above the disc surface. This process is known as slider "take-off".
A conventional air bearing surface includes a pair of raised side rails which face the disc surface. A taper is formed at the leading edges of the side rails, which acts as an aerodynamic ram for laminar flow generated by the rotating disc. An example of a leading edge taper is disclosed in Warner et al. U.S. Pat. No. 4,475,135. The taper is typically formed during an air bearing surface grinding and lapping process by tilting the slider, or a group of sliders, so that the leading edge of the slider is eroded with respect to the remaining air bearing surface and formed into the intended aerodynamic ram configuration. Since the air bearing surface is pressurized by the leading edge taper, variation in the taper angle and the position of the taper relative to other air bearing surface features causes the flying height of the transducer to vary. In addition, the flying height of the transducer typically varies proportionately more with variations in the manufacture of the taper than with other manufacturing variations.
There are three major difficulties associated with the conventional method of forming the leading edge taper. First, the angle of the taper with respect to the air bearing surface can be controlled only to the degree afforded by the mechanical tilting mechanism. Imprecision of the tilting mechanism introduces the greatest error in the intended angle at very shallow taper angles.
Second, the length of the taper and its position with respect to other air bearing surface features varies with the uncertainty in the grinding or lapping rate and with the tilt angle. The intersection between the leading taper and the air bearing surface has the greatest variability in location relative to other air bearing surface features, at shallow taper angles.
Third, conventional grinding or lapping processes permit only linear leading edge tapers. Also, the intersection between the taper and the air bearing surface is limited to a line which is parallel to the trailing edge of the slider. In addition, the surface of the lap plate limits the geometry of the taper area to a nearly planar surface since the taper area conforms to the surface of the lap plate. This also causes the taper area to be nearly perpendicular to the average laminar airflow direction.
The geometry of the leading taper, side rails and other air bearing surface features are designed to precisely control the flying height of the transducer over the rotating disc and to minimize friction between the slider and the disc. Limitations in the manufacturing control of very shallow taper angles eliminates from practical consideration air bearing configurations which provide superior control of the flying height. As a result, there is a continuing need for improved fabrication processes for forming leading edge tapers.